This invention relates generally to Nuclear Medicine imaging systems, and more particularly, to applications for imaging systems having multiple small-size imaging detectors.
Various diagnostic imaging systems are used to view tissue and function of organs within a patient's body. Several challenges exist, such as technologies which create planar images rather than a three dimensional (3D) dataset, the inability to prevent interference from other areas of the body, and low resolution which inhibits detection of small lesions. Some procedures are painful for the patient due to equipment and/or having to remain still for an extended period of time.
Mammography is one technology which is frequently used to screen for and detect lesions in breast tissue using 2D images. Unfortunately, mammography is painful and has low detection efficiency in dense breasts. Scintillation-mammography, or scinti-mammography, uses a gamma camera to acquire 2D images of breast tissue, but is also painful and cannot detect lesions near the chest wall. The lesions are typically quite small, such as less than 0.5 cm in diameter, and produce low signal; the gamma camera may not provide the high sensitivity and high spatial resolution needed. Also, background radiation from organs within the torso can make detection more difficult.
The breasts may also be imaged using a multi-bore collimator and single photon emission computed tomography (SPECT), but the acquisition time is long and the images have low spatial resolution. Also, positron emission tomography (PET) is useful, but both the equipment and radioisotope are expensive and thus are not a viable option for routine use.
Brain imaging is not as common as breast imaging but has some of the same challenges as high resolution is required to detect small lesions. The level of resolution is beyond what is currently possible in SPECT using the multi-bore collimator.
Gated cardiac imaging is a common procedure used to image the heart. Gated SPECT is acquired using detector(s) having multi-bore collimators. The detectors are rotated around the patient and views are acquired at multiple positions, for example, 90 views over 180 degrees. Each view is typically acquired for at least ten seconds, and the gamma camera may be synchronized to the patient's ECG.
The views are divided into time sections relating to heart pulse motion. R waves are detected, and each R to R interval may be divided into 8 phases. Each phase is then reconstructed separately. If the heart beats are irregular, it may not be possible to determine the R to R interval accurately and the gated data is discarded. If enough valid beats are not acquired, any reconstructed data may be incomplete, of poor quality, and/or result in artifacts.
Cardiac creep, the physiological motion of the heart after stress, also causes problems for conventional cardiac gamma camera acquisitions. As the detector rotates over time and acquires images from different directions, the heart slowly moves. Artifacts may be created in the image as the position of the heart in the first and last images is different. These artifacts may erroneously appear to be a defect when the problem is actually motion over time.
Therefore, a need exists for method and apparatus to image desired structures of interest in less time and with less pain than currently available techniques, while also providing improved resolution. Certain embodiments of the present invention are intended to meet these needs and other objectives that will become apparent from the description and drawings set forth below.